ABSTRACT
1. An enzyme-linked immunosorbent assay was used to determine the phospholipid specificity of antibodies in sera from 35 syphilis patients. 2. Based on the cross-reaction obtained aginst a mixture of cardiolipin, phosphatidylcholine and holesterol that is standard for flocculation tests according to the Venereal Disease Research Laboratory (CECON, Säo Paulo, Brazil), all 35 patients tested positive for antibodies of the IgG class whereas 13 (37%) also had IgM antibodies for the same mixture of lipids. IgG antibodies to cardiolipin were demonstrated in 2 patients (6%) and IgM antibodies in 5 (15%). Significant levels of IgG anti-phosphatidylcholine were detected in 3 patients (9%) and IgM antibodies in 4(11%). IgG anti-phosphatidylethanolamine antibodies were found in 1 patient (3%) and IgM antibodies in 3(9%). Antibody binding to cardiolipin plus cholesterol or cardiolipin plus phosphatidycholine was as effective as when the standard mixture of all 3 lipids was used. 3. A comparison with serum from systemic lupus erythematosus patients and inhibition studies using liposomes o cardiolipin or the mixture of 3 lipids suggests that there are at least 3 groups of anticardiolipin antibodies